Xerographic erase mechanism

ABSTRACT

Apparatus suitable for use in an automatic xerographic reproducing device for erasing a portion of the electrostatic charge recorded upon an imaged xerographic plate prior to the plate&#39;&#39;s development in order to prevent development from occuring in at least one margin (unimaged) region thereon. Further means are provided to adjust the size of the area erased in response to the size of the copy produced.

United States Patent 1191 Simmons Feb. 19, 1974 [5 XEROGRAPHIC ERASEMECHANISM 3,671,121 6/1972 Albert 355 7 [75] ento a y A S s Mac don NIY-3,540,806 11/1970 Starkweather 355/8 X Assigneelv Xerox Corporation,Stamford, Primary ExaminerJoseph F. Peters, Jr. m AssistantExaminer-Michael L. Gellner [22] Filed: May 12, 1972 l 21 Appl.N011252,698 [571 ABSTRACT Apparatus suitable for use in an automaticxero- 52 us. c1. 355/7, 355/74 graphic repwqucing device for erasingaPomon 51 Int. Cl G03g 15/06 the electmstatlc charge recmded maged 58Field of Search 355/3, 74, 7 mgraphic Plate the develoPmePt order toprevent development from occunng 1n at [56] Reerences Cited least onemargin (iuiirtnagedd) rtegtilon thereofntfurther rneans are won e o aJUS e s1ze o e area 3 556 655 E I PATENTS 35 /55 erased in response tothe size of the copy produced.

v ux et a 5 3,089,384 5/1963 Baasner 6 Claims, 5 Drawing FiguresPATENTED FEB I 9 I974 SHEH 3 0F 3 FIG. 4

XEROGRAPHIC ERASE MECHANISM ious processing stations. The plate is firstuniformly charged to a relatively high potential and the charge platesurface then exposed to a light image containing the original inputscene information to be reproduced. Under the influence of the lightimage, the charge carried on the plate surface is selectivelydissipatedin the light struck regions so as to record the original input sceneinformation thereon in the form of a latent electrostatic image. Thelatent image is made visible by applying specially preparedelectroscopic developer pow der, which is more generally known as toner,to the image bearing surface whereupon the toner particles areelectrically attracted and loosely held in the more highly chargedimaged areas thus rendering the electrical image visible.

Subsequent to the development operation, the visible toner image, whichis loosely adhering to the plate surface, is generally transferred fromthe plate surface to a sheet of final support material such as paper orthe like. One method for accomplishing image transfer is to place thefinal support sheet in overlying contact with the developed image andelectrically treating the back side of the sheet'with corona thuscausing the toner particles to be attracted from the plate surface tothe contacting side of the final support sheet. Toner particles carriedon the plate outside of the area contacted by the copy sheet, however,remain behind on the plate surface after completion of the transferoperation. This residual toner must be cleaned from the plate in somemanner before a new copying cycle is initiated in order to preventdegrading subsequent produced copy.

Heretofore, plate cleaning did not pose a serious problem in thexerographic art simply because the copy sheet was usually of a sizesufficient to cover the entire recorded original input scene informationand most machines did not possess the capability for developing thelarge charged but unused margin region lying outside the domain of theoriginal input scene information. However, with advances in thexerographic techniques, most of the newer xerographic copying machinesin use today have such a solid area developing capability. As

'a consequence, it is now possible to develop the charged but unusedmargins surrounding the recorded input scene. These margins develop outas relatively large areas of highly dense toner concentration. Cleaningof'this large mass of toner from the plate surface not only places aheavy burden on the machines cleaning system, but also produces a greatdeal of unwanted dirt within the machine environments and is costlybecause of the sheer amount of wasted toner involved.

To avoid the above noted problems in machines having a solid areadeveloping capability, erase lamps capable of discharging the platesurface in the initially charged but unimaged regions have been devised.Basically, this type oferase lamp is placed in a stationary position inregard to a moving photoconductive plate and the lamp is periodicallyenergized to irradiate predetermined regions on the plate. The intensityand spectral output of the lamp is adapted so that the charge level inthe irradiated zone is below the operating threshold level of thedeveloping system thus preventing development. For further details andinformation concerning this type of erase mechanism reference is had tocopending continuation application Ser. No. 145,013, filed in the nameof Donohue. Although the Donohue type erase system has proven to be anefficient discharge device when employed in the normal Xerographicenvironment, it nevertheless does not readily lend itself to use in amachine where the size of the input scene information may vary betweeneach imaging cycle.

It is therefore an object of the present invention to improve apparatusfor erasing an electrostatic charge from a xerographic plate. I

It is a further object of this invention to provide apparatus forerasing the unused margin region of an exposed xerographic plate priorto development.

It is yet another object of this invention to provide an adjustableerase lamp capable of erasing varying mar gin widths along the side of amoving xerographic plate in response to the size of the copy sheet inprocess.

-Yet another object of this invention is to minimize the amount ofunwanted development produced in an automatic xerographic reproducingmachine.

A still further object of this invention is to reduce the amount of dirtproduced in an automatic xerographic reroducing machine.

Yet another object of this invention is to reduce the amount of residualtoner left on the photoconductive plate surface subsequent to thetransferring of the image to a final support sheet.

These and other objects of the present invention are attained by meansof an erase lamp mechanism posi tioned adjacent to a moving xerographicplate having a latent image recorded thereon. A lamp is arranged toirradiate a selected region alongat least one margin lying outside theimaged area to dissipate the plate charge below a level sufficient tosustain development. A shade is movably interposed in light blockingrelationship between the erase lamp and the charged xerographic plate toblock at leasta part of the illumination from irradiating the chargedplate. The size of the copy sheet in process is sensed by means of asheet sensing mechanism which is adapted to preposition the shade inrelation to the lamp so that the charge in the unused margin region,that is, a region lying outside of the domain of the copy sheet, iserased prior to image development.

For a better understanding of the invention as well as other objects andfurther features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic view showing the erase mechanism of the presentinvention embodied within an automatic xerographic processing machine;

margin of the moving xerographic recording plate found in the automaticmachine illustrated in FIG. 1.

Referring now to the drawings, there is shown for the purposes ofexplanation an automatic xerographic reproducing machine incorporatingthe improved erase mechanism of the present invention. The copying ma- 7chine employs a drum-like member 10, the outer periphery of which isfurnished with a suitable xerographic imaging or photoconductivematerial 11 that is well-known and used to those skilled'in the art.Drum 10, which is suitably journaled for rotation within the machineframe by means ofa shaft 12, rotates in the direction indicated in FIG.1 to bring the photoconductive image retaining surface 11 thereon past aplurality of xerographic processing stations. Suitable drive means (notshown) are also provided to power and coordinate. the motion of thevarious cooperating machine components to produce a faithfulreproduction of the original input scene information.

I Since the practice of xerography is well-known in the art, the variousprocessing stations for producing a copy of the original are hereinrepresented as blocks A through E in FIG. 1. At station A, a uniformcharge is placed upon the photoconductive surface of the drum. Thecharged drum surface is then passed to an exposure station B where atleast a portion of the charged surface is exposed to a light image ofthe original input scene information so as to record the original inputscene information thereon in the form of a latent electrostatic image.Developing means for applying toner material to the image bearingsurface is provided at developing station C wherein the latent image ismadevisible. The developed image is then brought into moving contactwith a sheet of final support material 13 at a transfer station Dwherein the toner image is electrically removed from the plate surfaceand placed in image configuration upon the contacting side of the finalsupport sheet. Finally, at a cleaning station E, a cleaning mechanism,such as a fur brush or the like, is brought into operative contact withthe photoconductive plate surface and the residual toner removed fromthe plate thereby placing the xerographic plate in a condition such thatthe plate can be again used in the xerographic process. I

It is herein contemplated that the sheets of final support materialprocessed in the automatic xerographic reproducing device will be storedwithin the machine by means ofa removable paper cassette 14. It isfurther contemplated that the automatic reproducing machine will havethe capability of accepting and processing copy sheets of varyinglengths. The length of the copy sheet is dictated by the size of theoriginal recorded upon the photoconductive plate with variations inlength being perpendicular to the direction of sheet movement as itmoves through the machine. To this end, the paper cassette is providedwith an adjustable side margin so that sheets of varying lengths can beaccommodated therein. In practice, the cassette is filled with a stackof paper 15 of a preselected size and the cassette inserted into themachine by sliding the cassette along a base plate 16 which guides thecassette into operable relationship with a pair of feed rolls 17. Thefeed roll mechanism is arranged to operate upon the uppermost sheet inthe stack to separate the sheet from the remainder of the stack and toadvance the separated sheet towards the transfer station. A registrationmechanism 18 is interposed between the sheet supply station and thetransfer station. The mechanism is arranged to momentarily intercept theleading edge of a sheet moving between the stations so as to align andregister the sheet in relation to the developed xero' graphic imagerecorded on the drum surface. The copy sheet and the developed image arethen advanced together through the transfer station wherein the image isplaced upon the overlying sheet surface.

In operation, the top margin M of the xerographic image recorded uponthe drum surface is registered in close parallel alignment with theupper edge 19 of the drum surface as seen in FIG. 2. The top side marginof the supply tray is also aligned'parallel with the end of the drum bymeans of an upright fixed margin guide 20 which serves to register theone side edge of the stack with the top edge of the image recorded onthe drum. The right hand margin guide 21 of the cassette is adjustableso that the cassette can accommodate sheets of varying length therein.

The size of the copy sheet stored in the cassette is, of

course, dependent upon the size of the image recorded.

upon the xerographic drum. As can be seen, as the size of the recordedimage varies in length, the width of the initially charged but unusedmargin region (X) along the bottom edge of the drum will also vary.Ordinarily, in a machine having a solid area developing capability, thischarged but unimaged margin region will be developed with toner as thedrum moves through the developing station. However, this toner will notbe transferred to the final support sheet and will ultimately have to becleaned from the drum before a new imaging cycle is initiated. Thepresent invention is adapted to prevent this unwanted margin developmentfrom occurring and thus eliminating the added burden placed on thecleaning system as well as reducing the amount of dirt broadcastthroughout the machine.

Positioned between the image exposure station B and the developmentstation C is an erase lamp mechanism 25 capable of dissipating theinitial charge created along the unused right hand margin of the drum.As noted, this unused drum region typically is that area on the drumsurface which does not contain input data and as such does not come incontact with the copy sheet during transfer. By eliminating the chargein this unused region prior to development, the amount of plate cleaningnecessary after image transfer is minimized and the amount of developermaterial required for each development cycle is considerably reduced.

The erase mechanism includes an electroluminescent panel 26 (FIG. 5)supported adjacent to and in close within a rigid holder 27 which servesto uniformly position the panel at a predetermined distance above thephotosensitive surface. A shade member 28, the interior surface of whichcomplements the exterior surfaces of-the panel and panel holderassembly, slidably encloses the panel in light-tight relationshiptherein. In this manner, the shade can be laterally repositioned inregard to the lamp so that margins of varying width (X) can beirradiated along the edge of the drum.

The slidable shade 28 is operatively connected to a sheet'sensingcontrol mechanism 29, the operation of which will be explained ingreater detail below, by means of an inextensiblecord 30 which is lockedto the shade mechanism by suitable means as for example pin 35. Inoperation, the control mechanism senses the size or more particularlythe length of the copy sheet being processed and slidably positions theshade in relation to the stationary erase lamp so that this unusedmargin region on the drum is irradiated with radiation to substantiallyreduce the charge in this area. In practice, the charge is reduced to alevel below the development systems threshold potential level. As aresult, the margin region remains undeveloped as it is moved through thesubsequent developing station.

Referring more specifically to'FIGS. 2-4, there is illustrated a sheetsensing and control mechanism of the instant invention. The slidableshade 28 is normally mechanically biased to a rest position by means ofa spring element 37 anchored in the left hand frame 38 (FIG. 2) of themachine. The spring exerts a force upon the inextensible cord 24-tendingto pull the slide laterally along the lamp holder to a fully extendedposition against a stop 39 affixed in the lamp holder. Although the stopcan be stationed anywhere along the lamp holder, it is desirable thatit'be positioned in order to facilitate the smallest size exposurecontemplated for processing in the automatic machine.

As can be seen in FIG. 2, cord 30, after passing through the slidemechanism, passes over a pairof small guide pulleys 40 mounted in theright hand frame 41 of the machine and then around a larger pulley 43rotatably secured in horizontal mounting bracket 45 and finally the cordis secured to the free end of lever arm 46. The opposite end of thelever arm is movably supported within the sheet sensing mechanism of theinstant invention, herein generally referenced by the numeral 29.

The sheet sensing mechanism is supported above the paper supply cassetteupon the horizontal bracket 45 by means of a support bar 50 securedthereto in the manner best illustrated in FIGS. 3 and 4. Basically, thesensing mechanism generally includes a one way clutch mechanism 51, thepreviously noted lever arm 46, and a sheet sensing arm 52. The sheetsensing arm 52 is secured to the bottom portion of the clutch mechanismby means of a vertical shaft 54. A return spring 55 is wound about theshaft and is adapted to engage the sensing arm in a manner tocontinually urge the arm in a counter clockwise direction towards a homeposition wherein the sensing arm is normally positioned as illustratedin FIG. 3 with the free end of the arm extending beyond the adjustableright hand side margin guide 21 of the paper cassette.

A sensing arm actuator60 is rotatably pinned b means of a pivot 62 inthe adjustable right hand margin guide 21 of the cassette. A clearsquare shaped aperture 61 is cut in the actuator through which passes astationary pin 63 that is securely staked in the margin guide 21. Aspring 65, also affixed to the margin guide and is arranged tocontinually force the bottom wall of the square apertureinto contactagainst the pin thus tending to normally support the actuator face 66 ina substantially vertical position.

In operation, when a cassette is inserted into the machine, actuatorface 66 comes into moving contact with the free end of the sheet sendingarm causing the arm to swing about its stationary pivot point in aclockwise direction as seen in FIG. 3. However, prior to the cassettesreaching its operative position in relation to the feed rolls, theactuator face releases the sensing arm thus allowing the arm to returnto its normal home position. As can be seen, the degree of displacementof the sensing arm is dependent upon the position of the adjustablemargin guide 21 in relation to the sensing arm pivot point. Whenrelatively short sheets are stored in the stack the margin guide ispositioned further away from the pivot point than when long sheets arestored therein. As a consequence, the degree of displacement of arm 52is relatively small. Similarly when large sheets are stored in thecassette the margin guide is close to the pivot point and thedisplacement is relatively larger.

The movement of the sheet sensing arm is translated through the clutchmechanism to the lever arm 46 which is operatively attached to cord 30.As the sensing arm swings through its path of travel during theinsertion of a cassette into the machine, the lever arm is caused tofollow in a positive manner in'a clockwise direction. However, when theactuator face 66 releases the sensing arm, the clutch acts to lock thelever arm at its furthestmost point of rotation while, at the same time,freeing the sensing area to return to the home position. As can be seen,the position of the lever arm is therefore a direct indication of thesize of the copy sheet being processed in the machine. This informationis imparted directly to the shade mechanism via cord 30. By properlypositioning the various elements, such as the pulley placements, theamount of angular displacement of the lever arm can be directlyconverted mechanically into a lever displacement of the lamp shadewhereby a margin complimentary to the size of the copy sheet in processwill be erased upon the drum surface.

Upon the removal of the cassette from the machine frame, a dog 68engages a cam element 69 mounted on the sidewall of the cassette guide16. The cam and dog imparts a horizontal motion to a slide member 70.The slide member, in turn, engages a lug 71 on the clutch mechanismmounted on the side of the sensing mechanism which acts to disengage theclutch releasing the lever arm and permitting the arm to return to itsoriginal starting position. A profile 72, machined on the workingsurface of the dog, is generated so that no motion is imparted to theslide mechanism by the cam when the cassette is inserted into themachine.

While this invention has been described with reference to the structureherein disclosed, it is not confined to the details as set forth andthis application is intended to cover any modifications or changes thatmay come within the scope of the following claims.

What is claimed is:

1. A reproducing apparatus comprising: a photosensitive plate, means forforming a latent electrostatic image on said plate, means for reducingthe charge in at least one unused margin region of said plate, means fordeveloping said electrostatic latent image following said chargereduction in said marginal region, and means for transferring said imageto a sheet of final support material, the improvement wherein saidcharge reduction means comprises:

a source of radiation capable of reducing the charge within said atleast one margin region, said source being arranged to irradiate said atleast one margin region;

adjustable shade means movably interposed in block- .ing relationshipbetween said source and said plate to prevent at least partof theradiation from said source from irradiating said plate; and

means for adjusting the position of said shade in response to the sizeof the final support sheet.

2. An apparatus as in claim 1 wherein said shade is in slidingrelationship with said source.

3. An apparatus as in claim 2 wherein said source comprises anelectroluminescent lamp positioned adjacent to said plate.

4. in an automatic xerographic reproducing device of the type wherein adeveloped xerographic image is transferred from a moving photoreceptorsurface to a final support sheet, apparatus to erase the charge along atleast one side margin of the moving photoreceptor including,

an electroluminescent lamp positioned adjacent said moving member andbeing arranged to extend from one side margin of the member transversesaid member to irradiate said charged member to dissipate the charge inthe irradiated regions,

a movable shade mounted in light blocking relationship with said lampand being arranged to move transverse to the direction of movement ofsaid member whereby margins of varying widths are erasable on saidmember, and

means operable in response to the size of the final support sheet toposition said shade whereby the charge in the margin of said memberlying outside the imaged region is reduced to a level below the imageddevelopment level.

5. In an automatic xerographic reproducing apparatus of the type havingcharging means to uniformly charge the entire image retaining surface ofa moving photoconductive member, exposure means to selectively dissipatethe charge on the plate to record original input scene information inthe form ofa latent electrostatic image, the developing apparatus formaking the latent image visible, and means to transfer the developedimage to a sheet of final support material, the

improvement comprising,

an erase lamp positioned between the charging and vdeveloping meansbeing arranged to illuminate at least one margin of said member todissipate the charge thereon,

a movable shade arranged in light blocking relationship between the lampand said member to vary the width of the margin erased,

sensing means to detect width of the final support sheet in process, and

means operatively connected to said sensing means to position said shadein response to the width sensed whereby the charge along said one marginlying outside the imaged region is reduced to a level below the imagedevelopment level.

6. An automatic xerographic device of the type including means to move auniformly charged xerographic plate through a series of processingstations including an exposure station wherein a latent electrostaticimage is recorded on at least a portion of said plate surface, adevelopment station wherein finely divided marking particles areattracted into the highly charged imaged areas on said plate therebymaking the latent electrostatic image visible, and a transfer stationwherein the developed image is transferred to a sheet of final supportmaterial brought into moving contact with said plate, apparatus forpreventing unwanted development of the plate surface including an eraselamp positioned adjacent to the charged plate surface between theexposure station and the development station, said erase lamp beingarranged to illuminate at least a portion of said charged plate surfaceto reduce the charge found thereon to a level sufficient to preventdevelopment thereof,

a movable shade means interposed in light blocking relation between saiderase lamp and the charged plate surface to prevent at least part of theillumination from said lamp from irradiating said plate whereby thecharge on a preselected region of said plate is dissipated, and

control means to sense the size of the copy sheet moved into contactwith said moving plate surface and to regulate the positioning of saidmovable shade in relation to said lamp whereby the charge on the platesurface moving through the transfer station lying outside of the sheetcontact zone is reduced sufficiently to preclude subsequent develop-

1. A reproducing apparatus comprising: a photosensitive plate, means for forming a latent electrostatic image on said plate, means for reducing the charge in at least one unused margin region of said plate, means for developing said electrostatic latent image following said charge reduction in said marginal region, and means for transferring said image to a sheet of final support material, the improvement wherein said charge reduction means comprises: a source of radiation capable of reducing the charge within said at least one margin region, said source being arranged to irradiate said at least one margin region; adjustable shade means movably interposed in blocking relationship between said source and said plate to prevent at least part of the radiation from said source from irradiating said plate; and means for adjusting the position of said shade in response to the size of the final support sheet.
 2. An apparatus as in claim 1 wherein said shade is in sliding relationship with said source.
 3. An apparatus as in claim 2 wherein said source comprises an electroluminescent lamp positioned adjacent to said plate.
 4. In an automatic xerographic reproducing device of the type wherein a developed xerographic image is transferred from a moving photoreceptor surface to a final support sheet, apparatus to erase the charge along at least one side margin of the moving photoreceptor including, an electroluminescent lamp positioned adjacent said moving member and being arranged to extend from one side margin of the member transverse said member to irradiate said charged member to dissipate the charge in the irradiated regions, a movable shade mounted in light blocking relationship with said lamp and being arranged to move transverse to the direction of movement of said member whereby margins of varying widths are erasable on said member, and means operable in response to the size of the final support sheet to position said shade whereby the charge in the margin of said member lying outside the imaged region is reduced to a level below the imaged development level.
 5. In an automatic xerographic reproducing apparatus of the type having charging means to uniformly charge the entire image retaining surface of a moving photoconductive member, exposure means to selectively dissipate the charge on the plate to record original input scene information in the form of a latent electrostatic image, the developing apparatus for making the latent image visible, and means to transfEr the developed image to a sheet of final support material, the improvement comprising, an erase lamp positioned between the charging and developing means being arranged to illuminate at least one margin of said member to dissipate the charge thereon, a movable shade arranged in light blocking relationship between the lamp and said member to vary the width of the margin erased, sensing means to detect width of the final support sheet in process, and means operatively connected to said sensing means to position said shade in response to the width sensed whereby the charge along said one margin lying outside the imaged region is reduced to a level below the image development level.
 6. An automatic xerographic device of the type including means to move a uniformly charged xerographic plate through a series of processing stations including an exposure station wherein a latent electrostatic image is recorded on at least a portion of said plate surface, a development station wherein finely divided marking particles are attracted into the highly charged imaged areas on said plate thereby making the latent electrostatic image visible, and a transfer station wherein the developed image is transferred to a sheet of final support material brought into moving contact with said plate, apparatus for preventing unwanted development of the plate surface including an erase lamp positioned adjacent to the charged plate surface between the exposure station and the development station, said erase lamp being arranged to illuminate at least a portion of said charged plate surface to reduce the charge found thereon to a level sufficient to prevent development thereof, a movable shade means interposed in light blocking relation between said erase lamp and the charged plate surface to prevent at least part of the illumination from said lamp from irradiating said plate whereby the charge on a preselected region of said plate is dissipated, and control means to sense the size of the copy sheet moved into contact with said moving plate surface and to regulate the positioning of said movable shade in relation to said lamp whereby the charge on the plate surface moving through the transfer station lying outside of the sheet contact zone is reduced sufficiently to preclude subsequent development within this zone. 